In the Gigabit Ethernet MAC v4.0 core statistics, when the statistics are implemented in Block RAM, an issue affects the Fragment Frames Received statistics register (0x011) and the Undersize Frames Received statistics register (0x010). The behavior is as follows:
1. The Fragment Frames Received statistic increments by 256 every time the Undersize Frames Received statistic advances to a multiple of 256.
2. The Undersize Frames Received statistic (and consequently the Fragment Frames Received statistic) will continuously increment by 256 when an Undersize Frame is received, causing the counter to roll over to a multiple of 256. The counter will continue incrementing in this fashion until a new frame is received.
To resolve this issue, please install the patch for the v4.0 Gigabit Ethernet MAC core, which is available in the LogiCORE Gigabit Ethernet MAC v4.0 Release Notes (Xilinx Answer 18571).